1. Field of the Invention
The present invention relates to an instrument system mounted, for example, in a movable body such as a vehicle and a vessel, and in particular to a mounting structure of an indicating needle for the instrument system including an instrument unit and a measurement device, in which the indicating needle is attached to an output shaft of the instrument unit, the output shaft being operable to rotate in response to measurements obtained by the measuring device.
2. Description of the Related Art
A movable body such as a vehicle and a vessel incorporates an instrument system adapted to present information to a driver, the information obtained by measurement devices.
As the instrument system of this kind, for example, an analog-type instrument system is used that makes the indicating needle rotate on the basis of measurements obtained by the various measurement devices, and makes the indicating needle point to indications elements of a dial representing various conditions of the movable body, and thereby allows the measurements to be presented to the driver of the movable body.
The above analog-type instrument system may include (a) a box-shaped instrument case, (b) an instrument unit accommodated in the instrument case, (c) a dial provided on a front side of the instrument unit (i.e., on a side facing the driver), and accommodated in the instrument case, (d) indication elements provided on the dial indicative of the various conditions of the movable body, (e) an indicating needle arranged on the front side of the dial, (f) a light source arranged on a back side of the dial (i.e., on a distal side when viewed from the driver) and adapted to emit light illuminating the dial and the indicating needle, (g) a facing plate provided on the front side of the dial and adapted to cover the regions of the dial that is not involved in information indication, and (h) a transparent cover provided on the front side of the facing plate and configured to cover an opening of the instrument case.
The instrument unit includes an output shaft that rotates in response to measurements obtained by the measurement devices that measure the various conditions of the movable body. The indicating needle includes a mounting portion attached to the output shaft of the instrument unit, serving as a centre of rotation of the output shaft, and a pointer portion extending radially outward of the mounting portion. The indicating needle is configured to be rotated by the output shaft of the instrument unit and point to the indication elements of the dial by its pointer portion.
Also, the along-type instrument system includes a fixation structure for attaching the indicating needle to the output shaft of the instrument unit to secure the indicating needle to the output shaft.
As the fixation structure, various conventional fixation structures are advocated (for example, see Japanese Patent Application Laid-Open Publication No. H06-034399, hereafter referred to as the patent literature PTL 1).
Referring to FIG. 4, there is shown an exploded perspective view of the fixation structure adapted to secure the indicating needle to the output shaft of the conventional instrument unit disclosed in the patent literature PTL 1.
The fixation structure 40 illustrated in FIG. 4 includes a rotation-preventing feature 49 and a detachment-preventing feature 50 provided on an output shaft 42 of an instrument unit 41 and on a mounting portion 46 of an indicating needle 45 mounted to the output shaft 42.
The rotation-preventing feature 49 includes a plurality of flat portions 43 provided at an end of the output shaft of the instrument unit 41, and an insert hole 47 provided in a mounting portion 46 of the indicating needle 45 and is defined such that the output shaft 42 can be inserted thereinto.
The flat portions 43 define an outer circumference surface of the end of the output shaft 42, the end thus taking a quadrangular-prism-like shape. The insert hole 47 has a quadrangular planar shape defined such that the quadrangular-prism-like end of the output shaft 42 can be inserted into the insert hole 47.
The detachment-preventing feature 50 includes a protrusion 44 that protrudes at a base end of the output shaft 42 of the instrument unit 41; and an engagement hole 48 provided in the mounting portion 46 of the indicating needle 45 and is configured to be brought into engagement with the protrusion 44.
The protrusion 44 protrudes from the outer circumference surface of the output shaft 42 of the instrument unit 41.
The engagement hole 48 extends from an outer surface of the mounting portion 46 and communicates with the inner surface 47a of the insert hole 47.
In the fixation structure 40 with the above configuration, when the output shaft 42 of the instrument unit 41 is inserted into the insert hole 47 provided in the mounting portion 46 of the indicating needle 45, the flat portions 43 of the end of the output shaft 42 abut on the inner surface 47a of the insert hole 47 of the indicating needle 45. Also, the protrusion 44 at the base end of the output shaft 42 is brought into engagement with the engagement hole 48 of the mounting portion 46 of the indicating needle 45.
In the above-described manner, by virtue of the flat portions 43 of the output shaft 42 constituting the rotation-preventing feature 49, wherein the flat portions 43 abuts on the inner surface 47a of the insert hole 47 of the indicating needle 45, the fixation structure 40 prevents the output shaft 42 from rotating in and relative to the insert hole 47. Also, by virtue of the protrusion 44 of the output shaft 42 constituting the detachment-preventing feature 50, which is brought into engagement with the engagement hole 48 of the indicating needle 45, the fixation structure 40 prevents the output shaft 42 from being taken inadvertently out of the insert hole 47. In this manner, the indicating needle 45 is effectively secured to the output shaft 42 of the instrument unit 41.